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authorJarod Wilson <jarod@redhat.com>2011-05-11 15:14:31 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-05-20 16:21:22 -0300
commit08aeb7c9a42ab7aa8b53c8f7779ec58f860a565c (patch)
tree03bd9f53baecbc565adeb94c8a464cc97abc4411 /drivers/media/rc/rc-main.c
parent51ea62927e5bbb577360dd92c3f282edbf4cd3f8 (diff)
downloadop-kernel-dev-08aeb7c9a42ab7aa8b53c8f7779ec58f860a565c.zip
op-kernel-dev-08aeb7c9a42ab7aa8b53c8f7779ec58f860a565c.tar.gz
[media] rc: add locking to fix register/show race
When device_add is called in rc_register_device, the rc sysfs nodes show up, and there's a window in which ir-keytable can be launched via udev and trigger a show_protocols call, which runs without various rc_dev fields filled in yet. Add some locking around registration and store/show_protocols to prevent that from happening. The problem manifests thusly: [64692.957872] BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 [64692.957878] IP: [<ffffffffa036a4c1>] show_protocols+0x47/0xf1 [rc_core] [64692.957890] PGD 19cfc7067 PUD 19cfc6067 PMD 0 [64692.957894] Oops: 0000 [#1] SMP [64692.957897] last sysfs file: /sys/devices/pci0000:00/0000:00:03.1/usb3/3-1/3-1:1.0/rc/rc2/protocols [64692.957902] CPU 3 [64692.957903] Modules linked in: redrat3(+) ir_lirc_codec lirc_dev ir_sony_decoder ir_jvc_decoder ir_rc6_decoder ir_rc5_decoder rc_hauppauge ir_nec _decoder rc_core ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables snd_emu10k1_synth snd_emux_synth snd_seq_virmidi snd_seq_mi di_event snd_seq_midi_emul snd_emu10k1 snd_rawmidi snd_ac97_codec ac97_bus snd_seq snd_pcm snd_seq_device snd_timer snd_page_alloc snd_util_mem pcsp kr tg3 snd_hwdep emu10k1_gp snd amd64_edac_mod gameport edac_core soundcore edac_mce_amd k8temp shpchp i2c_piix4 lm63 e100 mii uinput ipv6 raid0 rai d1 ata_generic firewire_ohci pata_acpi firewire_core crc_itu_t sata_svw pata_serverworks floppy radeon ttm drm_kms_helper drm i2c_algo_bit i2c_core [last unloaded: redrat3] [64692.957949] [64692.957952] Pid: 12265, comm: ir-keytable Tainted: G M W 2.6.39-rc6+ #2 empty empty/TYAN Thunder K8HM S3892 [64692.957957] RIP: 0010:[<ffffffffa036a4c1>] [<ffffffffa036a4c1>] show_protocols+0x47/0xf1 [rc_core] [64692.957962] RSP: 0018:ffff880194509e38 EFLAGS: 00010202 [64692.957964] RAX: 0000000000000000 RBX: ffffffffa036d1e0 RCX: ffffffffa036a47a [64692.957966] RDX: ffff88019a84d000 RSI: ffffffffa036d1e0 RDI: ffff88019cf2f3f0 [64692.957969] RBP: ffff880194509e68 R08: 0000000000000002 R09: 0000000000000000 [64692.957971] R10: 0000000000000002 R11: 0000000000001617 R12: ffff88019a84d000 [64692.957973] R13: 0000000000001000 R14: ffff8801944d2e38 R15: ffff88019ce5f190 [64692.957976] FS: 00007f0a30c9a720(0000) GS:ffff88019fc00000(0000) knlGS:0000000000000000 [64692.957979] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [64692.957981] CR2: 0000000000000090 CR3: 000000019a8e0000 CR4: 00000000000006e0 [64692.957983] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [64692.957986] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [64692.957989] Process ir-keytable (pid: 12265, threadinfo ffff880194508000, task ffff88019a9fc720) [64692.957991] Stack: [64692.957992] 0000000000000002 ffffffffa036d1e0 ffff880194509f58 0000000000001000 [64692.957997] ffff8801944d2e38 ffff88019ce5f190 ffff880194509e98 ffffffff8131484b [64692.958001] ffffffff8118e923 ffffffff810e9b2f ffff880194509e98 ffff8801944d2e18 [64692.958005] Call Trace: [64692.958014] [<ffffffff8131484b>] dev_attr_show+0x27/0x4e [64692.958014] [<ffffffff8118e923>] ? sysfs_read_file+0x94/0x172 [64692.958014] [<ffffffff810e9b2f>] ? __get_free_pages+0x16/0x52 [64692.958014] [<ffffffff8118e94c>] sysfs_read_file+0xbd/0x172 [64692.958014] [<ffffffff8113205e>] vfs_read+0xac/0xf3 [64692.958014] [<ffffffff8113347b>] ? fget_light+0x3a/0xa1 [64692.958014] [<ffffffff811320f2>] sys_read+0x4d/0x74 [64692.958014] [<ffffffff814c19c2>] system_call_fastpath+0x16/0x1b Its a bit difficult to reproduce, but I'm fairly confident this has fixed the problem. Signed-off-by: Jarod Wilson <jarod@redhat.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media/rc/rc-main.c')
-rw-r--r--drivers/media/rc/rc-main.c47
1 files changed, 41 insertions, 6 deletions
diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
index a270664..0d4fcd9 100644
--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -749,6 +749,9 @@ static struct {
* it is trigged by reading /sys/class/rc/rc?/protocols.
* It returns the protocol names of supported protocols.
* Enabled protocols are printed in brackets.
+ *
+ * dev->lock is taken to guard against races between device
+ * registration, store_protocols and show_protocols.
*/
static ssize_t show_protocols(struct device *device,
struct device_attribute *mattr, char *buf)
@@ -762,6 +765,8 @@ static ssize_t show_protocols(struct device *device,
if (!dev)
return -EINVAL;
+ mutex_lock(&dev->lock);
+
if (dev->driver_type == RC_DRIVER_SCANCODE) {
enabled = dev->rc_map.rc_type;
allowed = dev->allowed_protos;
@@ -784,6 +789,9 @@ static ssize_t show_protocols(struct device *device,
if (tmp != buf)
tmp--;
*tmp = '\n';
+
+ mutex_unlock(&dev->lock);
+
return tmp + 1 - buf;
}
@@ -802,6 +810,9 @@ static ssize_t show_protocols(struct device *device,
* Writing "none" will disable all protocols.
* Returns -EINVAL if an invalid protocol combination or unknown protocol name
* is used, otherwise @len.
+ *
+ * dev->lock is taken to guard against races between device
+ * registration, store_protocols and show_protocols.
*/
static ssize_t store_protocols(struct device *device,
struct device_attribute *mattr,
@@ -815,18 +826,22 @@ static ssize_t store_protocols(struct device *device,
u64 mask;
int rc, i, count = 0;
unsigned long flags;
+ ssize_t ret;
/* Device is being removed */
if (!dev)
return -EINVAL;
+ mutex_lock(&dev->lock);
+
if (dev->driver_type == RC_DRIVER_SCANCODE)
type = dev->rc_map.rc_type;
else if (dev->raw)
type = dev->raw->enabled_protocols;
else {
IR_dprintk(1, "Protocol switching not supported\n");
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
while ((tmp = strsep((char **) &data, " \n")) != NULL) {
@@ -860,7 +875,8 @@ static ssize_t store_protocols(struct device *device,
}
if (i == ARRAY_SIZE(proto_names)) {
IR_dprintk(1, "Unknown protocol: '%s'\n", tmp);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
count++;
}
@@ -875,7 +891,8 @@ static ssize_t store_protocols(struct device *device,
if (!count) {
IR_dprintk(1, "Protocol not specified\n");
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
if (dev->change_protocol) {
@@ -883,7 +900,8 @@ static ssize_t store_protocols(struct device *device,
if (rc < 0) {
IR_dprintk(1, "Error setting protocols to 0x%llx\n",
(long long)type);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
}
@@ -898,7 +916,11 @@ static ssize_t store_protocols(struct device *device,
IR_dprintk(1, "Current protocol(s): 0x%llx\n",
(long long)type);
- return len;
+ ret = len;
+
+out:
+ mutex_unlock(&dev->lock);
+ return ret;
}
static void rc_dev_release(struct device *device)
@@ -974,6 +996,7 @@ struct rc_dev *rc_allocate_device(void)
spin_lock_init(&dev->rc_map.lock);
spin_lock_init(&dev->keylock);
+ mutex_init(&dev->lock);
setup_timer(&dev->timer_keyup, ir_timer_keyup, (unsigned long)dev);
dev->dev.type = &rc_dev_type;
@@ -1019,12 +1042,21 @@ int rc_register_device(struct rc_dev *dev)
if (dev->close)
dev->input_dev->close = ir_close;
+ /*
+ * Take the lock here, as the device sysfs node will appear
+ * when device_add() is called, which may trigger an ir-keytable udev
+ * rule, which will in turn call show_protocols and access either
+ * dev->rc_map.rc_type or dev->raw->enabled_protocols before it has
+ * been initialized.
+ */
+ mutex_lock(&dev->lock);
+
dev->devno = (unsigned long)(atomic_inc_return(&devno) - 1);
dev_set_name(&dev->dev, "rc%ld", dev->devno);
dev_set_drvdata(&dev->dev, dev);
rc = device_add(&dev->dev);
if (rc)
- return rc;
+ goto out_unlock;
rc = ir_setkeytable(dev, rc_map);
if (rc)
@@ -1058,6 +1090,7 @@ int rc_register_device(struct rc_dev *dev)
if (rc < 0)
goto out_input;
}
+ mutex_unlock(&dev->lock);
if (dev->change_protocol) {
rc = dev->change_protocol(dev, rc_map->rc_type);
@@ -1083,6 +1116,8 @@ out_table:
ir_free_table(&dev->rc_map);
out_dev:
device_del(&dev->dev);
+out_unlock:
+ mutex_unlock(&dev->lock);
return rc;
}
EXPORT_SYMBOL_GPL(rc_register_device);
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